1. Field of the Invention
This invention relates to a voice response system, and more particularly to a push button signal receiving device for use in a voice response system.
2. Description of the Prior Art
In general, a voice response system comprises a plurality of push button telephone terminals, a push button signal receiver which receives information formed of a push button signal (hereinbelow called "PB signal") from the telephone terminal, a central information processor (for example, a computer) which is driven by an output of the receiver, and a voice response unit which converts into voice a response sentence formed by the information processor and which transmits the response voice to the questioner's telephone terminal. Such voice response systems are typically used as in a seat reservation system of a passenger carrier, a stock quote system, etc.
Unlike signals made up of dial impulses, as used in conventional dial telephones, PB signals are composed of combinations of any two of four kinds of sine waves which are previously determined in each of two higher and lower regions of a voice frequency band. They are allotted to represent numerals and some special symbols. However, PB signals lie within the same signal frequency band as that of voice signals, and therefore, both these types of signals can coexist within the system, which sometimes creates a problem.
Like a PB signal receiver as used in an ordinary telephone exchange, a PB signal receiver employed in prior art voice response systems is so constructed that, in order to prevent a malfunction in the receiving of the PB signal resulting from confusion with the voice signal, the received PB signal is checked when a signal is received whose energy is distributed in a wide frequency band similar to a voice signal. On the other hand, in a system which is designed for effecting seat reservations employing a voice response system, and in which the desired purpose is achieved by the repetition of a push button input by a user and a response or instruction by the voice response unit, it is desirable to cut off the response voice when it becomes unwanted because it provides information already known or when it is desired to receive the next information with a push button request in the course of the response voice transmission, and thus shorten the required time of use of the whole system. With the prior art PB receiver, however, such objects cannot be accomplished.